In France, water electrolysis using renewable energy is nowadays considered a promising solution for producing hydrogen without dependencies on fossil fuels. Among different types, polymer electrolyte membrane water electrolysers (PEMWE) are considered the most favourable technology for hydrogen generation from renewable sources. However, the lifetime of current PEMWE technology is generally much shorter than the target value in Europe. Optimizing PEMWE operating parameters has been considered a potential approach to mitigate material degradation and extend the PEMWE lifetime, but it has been difficult so far because PEMWE degradation and its correlation to the performance and operating parameters involves complex multiscale physicochemical phenomena. Project DuraPEME contributes to improve the durability of PEMWE by developing an artificial intelligence (AI)-accelerated multiscale degradation model. In parallel and in connection with the models developed, it will also propose accelerated stress tests for PEMWE. We will achieve this goal by 1) characterizing degradations from multiple scales; 2) developing and accelerating a multiscale degradation model 3) generalizing the model in different uses and powers. The project will adopt a highly interdisciplinary approach by integrating methods in PEMWE multiphysics, material science, numerical calculation, and machine learning. As outcomes, project DuraPEME will empower PEMWE technology with an efficient multiscale degradation model. The model will enable optimizing PEMWE operating parameters to mitigate degradations.

Every year, more than 200 000 orthopaedic prostheses (knee, hip) and a huge (but unknown) number of dental implants are implanted in France. For an optimal efficiency, these implants have to be well integrated in bone. To favour osseointegration, dental implants rely on modification of their surface morphology, while a Calcium-Phosphate coating is often required on the surface of orthopaedic implants. Traditionally, these coatings are fabricated by plasma-spray, leading to well crystallized films in the most stable phases (mainly hydroxyapatite).Even though these plasma-sprayed coatings are commonly used on stems and metal-backs of hip prostheses, their efficiency is subject to controversy because of several drawbacks such as the excessive thickness of the coatings, their possible delamination leading to local inflammations, and the overly stable nature of the constitutive materials that do not favour reactivity. DECaP project aims at developing alternative coating techniques, less costly and leading more efficient coatings (with higher adhesion to substrate, more reactive to allow faster bone ongrowth and faster healing of the patient) potentially applicable to both dental and orthopaedic implants. The consortium will thus use ElectroSpinning (ES) and Electrostatic Spray Deposition (ESD) to fabricate (and characterize) osseoconductive coatings of optimized architectures, compositions and structures (amorphous or crystalline), on biomedical grade titanium substrates. We will aim at biologically reactive coatings such as out-of-equilibrium or amorphous calcium phosphates (highly difficult to stabilize as coatings by any other technique, thus their potential as osseoconductive coatings could never be assessed) or bioactive glasses (whose synthesis has never been attempted using ESD). Moreover, we will look for architectures that promote reactivity and mechanical adhesion to bone tissues: dense coatings with arborescent surface, and porous coatings with a large amount of porosity (easily obtained with ES), or even with a multiscale architecture (network of tubular pores inside a coral-like dense matrix). As a proof of concept, these findings will be applied to a real dental implant. The expected outputs of this project are: - Scientific: obtaining stable over time, out-of-equilibrium, reactive CaP or bioactive glass phases is a scientific challenge. Understanding how these phases are stabilized during the process could open the way to new materials with original properties (reactivity, transport…) - Industrial: after further development, the findings of DECaP project will allow biomaterial companies to implement new processes leading to innovative and efficient coatings for improved osseoconductivity of biomedical implants. - Societal: the improved osseoconductiviy of these implants will allow faster healing of the patients, thus better comfort, shorter treatments thus lower treatment cost and hopefully better long term success. Besides these cheaper coatings will help reduce the price of implants. DECaP consortium combines the competencies of three laboratories: MATEIS will bring its knowledge of calcium phosphates and extensive, in-situ characterization. LEPMI will use its in-depth understanding and practice of Electrostatic Spray Deposition, already applied with great success to the fabrication of Solid Oxide Fuel Cell components. LMI masters Electro Spinning, that was used (combined with sol-gel chemistry) to fabricate original and architectured materials.The synergy between the three laboratories will allow reaching our ambitious goals.

The challenge of the DURACELL project is to improve the durability of PEM fuel cells by optimizing the mechanical properties of the interfaces within the membrane-electrode assemblies (MEAs), where the electrochemical reactions take place. The latter are subjected to complex and variable mechanical stresses depending on the hygrothermal conditions related to the operation of the fuel cell, which can lead to the damage of its components and the shutdown of the system. The initial objective of the project will be to measure, identify and control the manufacturing parameters of the MEA that impact the adhesion between its layers. To that goal, specific mechanical characterizations will be implemented in order to quantify the level of adhesion at the interfaces of MEAs manufactured within the DURACELL project consortium. The measured properties will then be implemented in a numerical model in order to contribute to the prediction of the optimal physical properties of the MEA and its assembly conditions to limit the mechanical damage of its components. These results will be verified by comparing the lifetime of MEAs assembled under these different adhesion conditions, via in situ and ex situ accelerated stress tests (hygrothermal cycling and coupled mechanical/chemical degradation). These different tests will provide a better understanding of the mechanical/chemical degradation synergies that occur in the membrane and at the membrane|electrode|gas diffusion layers interfaces. They will also allow to unbundle the different mechanisms responsible for the degradation of MEAs in a system environment. The analysis of the results of the DURACELL project will lead to recommendations to be shared with the scientific and industrial community to limit the level of mechanical stresses undergone by the different components of a PEMFC, thus contributing to the increase of its life span in operation.

Within the context of energy shift towards a decrease in the contribution of fossil fuels, the development of new stationary energy storage systems is mandatory. Indeed, the intrinsic intermittent and variable nature of renewable energy sources, such as windmill and photovoltaic, require energy storage. Redox-flow batteries, allowing a decoupling of energy and power, are well adapted to such requirements. As a matter of fact, this technology presents advantages as compared to Li-ion systems presently under development for such applications, in particular for security and recyclability issues. However, the most advanced redox-flow batteries (Vanadium redox-flow batteries, studied since the 80’s) remain expensive with limitations in terms of stability and capacities. The present project aims at developing a full redox-flow battery, based on the flow of redox-mediators based aqueous solutions (pH around 7), using sodium insertion materials immobilized in the battery tanks. The use of these insertion materials will allow an increase in the energy density of these systems, and thus to potentially reduce their size. These materials will be free of toxic or expensive metallic element. To perform these research studies, we created a multidisciplinary team which will allow to break the technological locks related to the development of such innovative and performing systems. The project partners will pursue in particular the study and development of a pilot battery so as to demonstrate the potentialities of this approach for electrochemical energy storage at large scale (coupling with windmill and photovoltaic systems), with storage time of the order of a dozen hours.

The necessary reduction of greenhouse gases emissions, as a worldwide concern, should more than ever motivate us to find alternatives to fossil resources as well as adapted energy conversion processes. Among others, fuel cells will play a strategic role during the energy transition to come, and are likely to become a key player in the future energy mix. Proton Exchange Membrane Fuel Cells (PEMFC) are no doubt the most versatile (polyvalent) since they can meet many needs, across a wide range of power (from mW for portable applications to MW for stationary through dozens of kW for transport). In 2012, PEMFCs accounted for 88% of the shipments (457,000 units) and 41% of the megawatts shipped (166.7 MW). A major concern in PEMFC development, especially in the transport sector, is to increase their operation temperature above 100°C while decreasing the relative humidity conditions. Today, the operating temperature is still limited by the electrolyte used in the membrane-electrodes assemblies (MEAs). In COMEHTE, we propose to take benefit from clays hygroscopic properties to develop new composite membranes based on microfibrous sepiolite and tubular halloysite. These clays will be functionalized in order to direct the membrane morphology at the nanoscale, i) to make them proton conductive (addition of acid groups) and ii) to favor the interaction with Nafion®, the host matrix (addition of fluorinated groups). The particular elongated morphology of such clays will participate to improving the mechanical strength of the composite membrane. This approach will be coupled with the development of active nanofibre reinforcements to further improve the membrane mechanical resistance and with the incorporation of radical scavengers to limit the membrane degradation. The composite materials will also be used as the proton conductor in catalytic layers so as to optimize the membrane-electrode interface. Chemical functionalization, plasma activation and thermal complexation will be studied as three complementary routes to modify raw materials. Silane based precursors will be used to efficiently react with the numerous hydroxyl groups covering both inner and outer surfaces of the selected clays. Neutral or reactive plasma will be applied either to create reactive radicals to favor the chemical post-functionalization or to directly functionalize the treated clays. Thermal complexation will notably help dispersing the loads in the polymer matrix. Dedicated characterizations will be performed so as to identify the proper treatment routes and to select the most promising composites. The selection will be realized on different criteria such as the ion exchange capacity, the proton conductivity, the swelling, the thermomechanical resistance or the thermochemical stability. The selected materials will then be used to prepare membrane-electrodes assemblies (MEAs) from membranes and electrodes developed in the project. MEAs will be tested in severe conditions (intermediate temperature and low relative humidity, accelerated stress tests) in comparison to reference MEAs. The most promising MEAs will finally be tested in short stack configuration, following automotive test cycles.